This invention generally relates to pneumatic motors, and more particularly to pneumatic shift reciprocating motors for pneumatic piston pumps.
Pneumatic shift reciprocating motors are known with an example being shown in commonly assigned U.S. Pat. No. 5,586,480, issued Dec. 24, 1996 to the inventor of the present invention, the disclosure of which is incorporated by reference herein. U.S. Pat. No. 5,586,480 discloses a pneumatic motor having a piston chamber with a major piston and two valve chambers having three-way spool valves located therein. Operation of the piston is accomplished by alternately connecting opposite ends of the piston chamber to a pressurized air inlet or to exhaust. Shifting of the three-way spool valves is accomplished pneumatically by air that is supplied to an annular piston chamber continuously throughout the motion of the piston. Because the annular piston chamber was always connected to an air supply, the length of the major piston was the length of the stroke length, thereby causing such pneumatic motors to have longer overall lengths. This in turn created a motor having a less compact design and having longer internal air passages located therein. Additionally, the three-way spool valves as constructed therein contained multiple component parts including seals and also internal air passages to supply air to the end of the spools. The foregoing illustrates limitations known to exist in present pneumatic devices. Thus it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly an alternative pneumatic motor is provided including the features more fully disclosed hereinafter.
A pneumatic motor having a motor body having a main piston chamber with opposed first and second chamber ends, at least two spool chambers in fluid communication with the main piston chamber, an inlet for flowing a pressurized fluid into each of the at least two spool chambers, and an outlet provided in the housing for exhausting the pressurized fluid from the main piston chamber and each of the spool chambers. At least two spool members are in the two spool chambers, with each spool member adapted to be movable in a first direction to permit pressurized fluid to be supplied to the main piston chamber and also in a second direction to permit the pressurized fluid to be exhausted from the main piston chamber. A piston member is movable in a reciprocating manner in the main piston chamber in response to movement by the spool members. The piston has first and second piston ends and an annular piston chamber located between and in fluid communication with the first and second chamber ends, the first and second piston ends defining, with the first and second chamber ends, a first chamber and a second chamber, respectively, in the main piston chamber during reciprocation of the piston. First and second seals between the piston ends and the annular piston chamber are provided such that while the piston reciprocates within the main piston chamber, the first and second seals alternately exhaust the first and second chambers into the annular piston chamber.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with accompanying drawing figures.